An observational study in Rectal Cancer, sponsored by Maastricht Radiation Oncology. Recruiting at 3 sites in Netherlands. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-10-09.
Sponsored by Maastricht Radiation Oncology · Observational
The aim of the study is to provide prospective data regarding microscopic tumor spread in all directions from the macroscopic tumor in pathology specimens, as seen by eye, and on imaging to define the target volume for endoluminal radiation boosting in rectal cancer patients.
This study is a prospective multicentre cohort trial in ≥50 patients with a residual ycT1-3N0 tumor after neoadjuvant chemoradiotherapy or radiotherapy for rectal adenocarcinoma at least 6 weeks after the neoadjuvant treatment.
In addition to standard workup and treatment (e.g. a flexible endoscopy and an MRI scan at 6-8 weeks post-neoadjuvant therapy), patients will undergo pre-operatively, after induction of general anaesthesia, an endorectal ultrasound and rigid rectoscopy as study procedures if these procedures are not already part of standard workup. Furthermore, the pathological specimens of some patients will be scanned using MR imaging during certain parts of the pathological process.
Objectives include determining the maximum distance of microscopic tumor spread per patient in all directions, creating a tissue deformation model to account for changes due to e.g. fixation and pathological processing, using this tissue deformation model to translate the microscopic tumor spread back to the in vivo situation (e.g. back to in vivo MRI scans, 3D endo-ultrasounds), and evaluating/determining risk factors for the presence and/or extent of microscopic tumor spread.
This data will be used for target volume definition in rectal endoluminal radiation boosting.
2,400 studies on the registry are indexed under Rectal Neoplasms; 587 are open to participants now.
This study's planned enrollment of 50 is below the median of 161 across 498 observational studies indexed under Rectal Neoplasms.
Browse Rectal Neoplasms studies →Maastricht Radiation Oncology is the lead sponsor of 106 studies on the registry; 9 are open to participants now.
Counted across the registry records on this site, refreshed daily.
Patients with a limited (ycT1-3N0) residual tumor after neoadjuvant radiotherapy or long-course chemoradiotherapy for rectal adenocarcinoma.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
(*)= as determined by clinical assessment (digital rectal examination, endoscopy with or without ) and/or MRI. Biopsy/histology around the time of diagnosis is adequate; no biopsy/histology is needed after neoadjuvant therapy.
(**)= including tumor regrowths/local recurrence after an initial clinical complete response and a "watch and wait" approach. These patients will also be included after the local recurrence has been determined using endoscopy and/or MRI.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Neoadjuvant treatment is given before the main treatment (usually surgery), often to shrink a tumour. Adjuvant treatment is given after it, to lower the chance of the cancer coming back.
A biopsy takes a small piece of tissue to examine. “Archival tissue” is a sample already taken, for example at diagnosis, and kept by the hospital.
Whether a stored sample will do depends on when it was taken, how much there is and what the study needs. Ask whether the study accepts your stored sample or needs a new biopsy.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Adjuvant and neoadjuvant
Neoadjuvant treatment is given before the main treatment (usually surgery), often to shrink a tumour. Adjuvant treatment is given after it, to lower the chance of the cancer coming back.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Biopsy and archival tissue
A biopsy takes a small piece of tissue to examine. “Archival tissue” is a sample already taken, for example at diagnosis, and kept by the hospital.
Whether a stored sample will do depends on when it was taken, how much there is and what the study needs. Ask whether the study accepts your stored sample or needs a new biopsy.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
In addition to standard workup and treatment, patients will undergo pre-operatively, after induction of general anaesthesia, an endorectal ultrasound and rigid rectoscopy as study procedures if these are not part of standard workup yet.
Diagnostic Test: Ultrasound · Diagnostic Test: Rectoscopy · Other: Scan, e.g. CT (resection specimen)
3D endorectal ultrasound.
Rigid rectoscopy.
For some patients, images of the resection specimen (note: NOT of the patients) during the pathological process will be acquired.
Maximum distance of microscopic tumor spread per patient in all directions from the macroscopic tumor remnant in the pathology specimen
The maximum distance of microscopic tumor spread in all directions from the macroscopic remnant in the specimen will be measured per patient in millimeters by the pathology department in the pathologic resection specimens.
Time frame: During post-resection pathological analysis (i.e. approximately 14 days post-resection)
Maximum distance of microscopic tumor spread per patient from the macroscopic tumor remnant in the pathology specimen, reported separately for MTS perpendicular to the bowel wall and for MTS parallel to the bowel wall
Measured per patient in millimeters by the pathology department in the pathologic resection specimens. Microscopic tumor spread perpendicular to the bowel wall and parallel to the bowel wall will be reported separately.
Time frame: During post-resection pathological analysis (i.e. approximately 14 days post-resection)
Maximum distance of microscopic tumor spread per patient in all directions from the macroscopic tumor remnant in the pathology specimen excluding ypT0 patients
Measured per patient in millimeters by the pathology department in the pathologic resection specimens. For this secondary outcome, this will be reported excluding all ypT0 patients.
Time frame: During post-resection pathological analysis (i.e. approximately 14 days post-resection)
Maximum distance of microscopic tumor spread per patient in all directions from the macroscopic tumor remnant in the pathology specimen only including patients with microscopic tumor spread
Measured per patient in millimeters by the pathology department in the pathologic resection specimens. For this secondary outcome, this will be reported only for patients with microscopic tumor spread.
Time frame: During post-resection pathological analysis (i.e. approximately 14 days post-resection)
Maximum distance of microscopic tumor spread per patient in all directions from the macroscopic tumor remnant in the pathology specimen only for patients with regrowths
Measured per patient in millimeters by the pathology department in the pathologic resection specimens. For this secondary outcome, this will be reported only for patients with regrowths.
Time frame: During post-resection pathological analysis (i.e. approximately 14 days post-resection)
Tissue deformation factor/model to compensate for tissue deformation due to removal of the specimen from the body, formalin fixation and tissue processing at the pathology department
The deidentified images of the flexible endoscopy and in vivo MRI scan will be collected for the study. During the certain parts of the pathologic process, e.g. before and after fixation, MRIs of the pathological specimens of some of the patients will be made. These deidentified images of the specimens, together with e.g. the deidentified endoscopic, rectoscopic, ultrasound and in vivo MR images and possibly with optical images taken during pathological analysis, will be used to develop the deformation model. The flexible endoscopy and in vivo MRI scan are both taken approximately 6-8 weeks post-neoadjuvant treatment. The images of the rigid rectoscopy and 3D endorectal ultrasound are taken directly before TME surgery.
Time frame: The tissue deformation model will be created once all required data (e.g. MRI scans, rectoscopy images, endorectal ultrasound images) is available (approximately 14 days post-surgery for the final included patient).
Maximum distance of microscopic tumor spread per patient in all directions from the macroscopic tumor remnant as seen by eye and/or on imaging
The tissue deformation factor/model and the location of the microscopic tumor spread in relation to the macroscopic remnant determined during pathological analysis, will be used to determine the maximum distance of microscopic tumor spread in relation to the macroscopic tumor as seen by eye (rectoscopically/endoscopically) and/or on imaging (endo-ultrasound, MRI) per patient in all directions. The flexible endoscopy and in vivo MRI scan are both taken approximately 6-8 weeks post-neoadjuvant treatment. The images of the rigid rectoscopy and 3D endorectal ultrasound are taken directly before TME surgery.
Time frame: When the tissue deformation model is finished (approximately 3 months after all data for every patient is available). For the imaging time frames: please refer to the description.
Treatment margin (in the various directions) relative to the macroscopic tumor to cover 90% and 95% of all microscopic tumor spread
Distance that covers the microscopic tumor spread in all directions in millimeters for 90 and 95% of patients, including 95% confidence intervals, both reported including and excluding ypT0 patients. Reported both by eye and on imaging, for which among others the tissue deformation model will be used.
Time frame: Once the microscopic tumor spread is determined for all patients (approximately 14 days post-surgery for the final included patient), the treatment margins will be calculated.
Evaluation of risk factors for the presence and/or the extent of microscopic tumor spread identified by the meta-analysis we performed
These risk factors include pathological T stage after chemoradiation (ypT stage) and time interval between neoadjuvant chemoradiotherapy and surgery.
Time frame: ypT stage is determined during post-resection pathological analysis (i.e. approximately 14 days post-resection). The time interval is determined at the day of surgery.
Identification of potential risk factors for the presence and the extent of microscopic tumor spread not yet identified by our meta-analysis
Potential risk factors include among others ycT stage, regrowths/local recurrence, diameter, predominant histologic grade, tumor regression score/grade (pathologically), vascular invasion, lymphatic invasion, perineural invasion, microsatellite instability (MSI) and parameters related to in vivo MR imaging.
Time frame: Most are determined during post-resection path. analysis (approx. 14 days post-resection). ycT stage is determined approx. 6-10 weeks post-neoadjuvant treatment (multidisciplinary team), in vivo imaging is done approx 6-8 weeks post-neoadjuvant treatment
Analysis of (re)biopsy material
This includes the biopsy material at time of diagnosis, and also the rebiopsy material for patients with tumor regrowths/local recurrence after an initial clinical complete response and a "watch and wait" approach. These (re)biopsies are a part of the standard diagnostic work-up. Part of this analysis will be performed during this study by reassessment of the histology of the biopsy material and/or if applicable the rebiopsy material.
Time frame: Biopsy material is obtained at time of diagnosis.
Plan to share: No — The data will not be shared with other researchers, however the following applies if patients have given specific, additional consent: If patients have consented to the use of leftover body material and/or data in further studies, the deidentified images (endoscopy, rectoscopy, ultrasound, in vivo MRIs and specimen MRIs) and pathological specimens/samples including (re)biopsies, and the accompanying data can be used for further scientific research related to rectal cancer by the investigators, including investigators from collaborating institutions, without requiring additional informed consent.
Started Aug 2022 (actual). Primary completion is estimated for May 2027, 57 months after the start.
Of 213 non-industry observational studies under Rectal Neoplasms, half reached primary completion within 47 months of starting (the median), counting those still running; a quarter within 24 and three quarters within 116. This study's planned 57 months is above that.
Counting every sponsor, half of 228 studies reached it within 45 months; a quarter within 24 and three quarters within 116.
How these figures are worked out, and which studies are left out of them.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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